So, I had the great fortune of running into a rally organizer while I was in DC on the 6th. While he was not running this particular rally, he had ran many events over the past 20 years, and did have friends that were organizing this event. He was literally texting with them back and forth while we were waiting for Trump to come out (before the cell signal got spotty).
He was an older gentleman, and offered me a lot of insight. One way that they count the attendance of an event is based on how many blocks it fills in DC. When we were at the Capitol building, he told me that that front lawn could hold 75,000 people. He also told me that from the end of the reflecting pool, if it filled all the way back to the monument, that was 1-2 million people. And each block beyond that is another 500,000. He estimated, based on crowd size, that there was at least 3 million people there.
While he was not running the event, he said that one of the reasons he came out is because he wanted to analyze this new strategy of crowd deployment. Utilizing social media to reach viewers never thought possible.
He told me to get a crowd of about a million people typically takes about 18 months of planning, and that he was amazed that such a massive crowd was drawn to DC in such a short period of time.
He also stated that in all of his years working in DC, he has never seen this many people.
I've yet to see any reports on the crowd size. Other than some articles saying a few 100 thousand were at the Capitol. https://ibb.co/rMZ3znr